Cookies on the NHS website
We've put some small files called cookies on your device to make our site work.
We'd also like to use analytics cookies. These send information about how our site is used to services called Adobe Analytics, Hotjar and Google Analytics. We use this information to improve our site.
Let us know if this is OK. We'll use a cookie to save your choice. You can read more about our cookies before you choose.
I'm OK with analytics cookies Do not use analytics cookies
Search the NHS website
Search
Health A-Z
Live Well
Mental health
Care and support
Pregnancy
Browse
More
Home Health A to Z
Schistosomiasis (bilharzia)
Schistosomiasis, also known as bilharzia, is an infection caused by a parasitic worm that lives in fresh water in subtropical and tropical regions.
The parasite is most commonly found throughout Africa, but also lives in parts of South America, the Caribbean, the Middle East and Asia.
Travel Health Pro has a map of where schistosomiasis is found
You often don't have any symptoms when you first become infected with schistosomiasis, but the parasite can remain in the body for many years and cause damage to organs such as the bladder, kidneys and liver.
The infection can be easily treated with a short course of medicine, so see your GP if you think you might have it.
How you get schistosomiasis
The worms that cause schistosomiasis live in fresh water, such as:
ponds
lakes
rivers
reservoirs
canals
Showers that take unfiltered water directly from lakes or rivers may also spread the infection, but the worms aren't found in the sea, chlorinated swimming pools or properly treated water supplies.
You can become infected if you come into contact with contaminated water – for example, when paddling, swimming or washing – and the tiny worms burrow into your skin.
Once in your body, the worms move through your blood to areas such as the liver and bowel.
After a few weeks, the worms start to lay eggs. Some eggs remain inside the body and are attacked by the immune system, while some are passed out in the person's pee or poo.
Without treatment, the worms can keep laying eggs for several years.
If the eggs pass out of the body into water, they release tiny larvae that need to grow inside freshwater snails for a few weeks before they're able to infect another person. 
This means it's not possible to catch the infection from someone else who has it.
Symptoms of schistosomiasis
Many people with schistosomiasis don't have any symptoms, or don't experience any for several months or even years.
You probably won't notice that you've been infected, although occasionally people get small, itchy red bumps on their skin for a few days where the worms burrowed in.
After a few weeks, some people develop:
a high temperature (fever)
an itchy, red, blotchy and raised rash
a cough
diarrhoea
muscle and joint pain
tummy pain
a general sense of feeling unwell
These symptoms, known as acute schistosomiasis, often get better by themselves within a few weeks.
But it's still important to get treated because the parasite can remain in your body and lead to long-term problems.
Long-term problems caused by schistosomiasis
Some people with schistosomiasis, regardless of whether they had any initial symptoms or not, eventually develop more serious problems in parts of the body the eggs have travelled to.
This is known as chronic schistosomiasis.
Chronic schistosomiasis can include a range of symptoms and problems, depending on the exact area that's infected.
For example, an infection in the:
digestive system can cause anaemia, tummy pain and swelling, diarrhoea and blood in your poo
urinary system can cause irritation of the bladder (cystitis), pain when peeing, a frequent need to pee, and blood in your pee
heart and lungs can cause a persistent cough, wheezing, shortness of breath and coughing up blood
nervous system or brain can cause seizures (fits), headaches, weakness and numbness in your legs, and dizziness
Without treatment, affected organs can become permanently damaged.
When to seek medical advice
Visit your GP if you develop the symptoms above and you've travelled in parts of the world where schistosomiasis is found, or if you're concerned that you may have been exposed to the parasites while travelling.
Tell your GP about your travel history and whether you think you may have been exposed to potentially contaminated water.
If your GP suspects schistosomiasis, they may refer you to an expert in tropical diseases.
The diagnosis is usually made by finding eggs in a sample of your pee or poo. You may also be diagnosed by a blood test.
Treatments for schistosomiasis
Schistosomiasis can usually be treated successfully with a short course of a medication called praziquantel, which kills the worms.
Praziquantel is most effective once the worms have grown a bit, so treatment may need to be repeated a few weeks after your first dose.
Steroid medication can also be used to help relieve the symptoms of acute schistosomiasis, or symptoms caused by damage to the brain or nervous system.
Preventing schistosomiasis
There's no vaccine for schistosomiasis, so it's important to be aware of the risks and take precautions to avoid exposure to contaminated water.
You can check whether the area you're visiting is known to have a problem with schistosomiasis using Travel Health Pro's country information section.
If you're visiting one of these areas:
avoid paddling, swimming and washing in fresh water – only swim in the sea or chlorinated swimming pools
boil or filter water before drinking – as the parasites could burrow into your lips or mouth if you drink contaminated water
avoid medicines sold locally that are advertised to treat or prevent schistosomiasis – these are often either fake, sub-standard, ineffective or not given at the correct dosage
don't rely on assurances from hotels, tourist boards or similar that a particular stretch of water is safe – try to find out from an official or reliable source
Quickly drying yourself with a towel after getting out of the water is not a reliable way of preventing infection, although it's a good idea to dry yourself as soon as possible if you're accidentally exposed to potentially contaminated water.
Page last reviewed: 17 December 2021
Next review due: 17 December 2024
Support links
Home
Health A to Z
Live Well
Mental health
Care and support
Pregnancy
NHS services
Coronavirus (COVID-19)
NHS App
Find my NHS number
Your health records
About the NHS
Healthcare abroad
Contact us
Other NHS websites
Profile editor login
About us
Accessibility statement
Our policies
Cookies
© Crown copyright